Heretofore, in noncontact type tonometers, as alignment verification, the vertical and horizontal positions of optical systems of an apparatus body were verified with respect to the eye and the working distance between the eye and a nozzle for discharging fluid toward the eye was verified. In conventional the noncontact type tonometers, an alignment target light may be projected toward the eye from the axial direction of the nozzle in order to verify the alignment. Noncontact type tonometers of this type are designed such that upon verification of the alignment, fluid, such as air pulse or the like, is discharged from the nozzle to transfigure the cornea of the eye and measure the intraocular pressure thereof. (e.g., Japanese Patent Publication No. Sho 56-6772).
However, in conventional noncontact type tonometers of this type, an alignment target light, when the alignment is proper, is made incident to the cornea of the eye from the perpendicular direction as if the alignment target light is converged to the center of curvature of the cornea to form a virtual image. The virtual image is reimaged on a reticle plate, and then the alignment is determined from the sharpness of the reimaged virtual image and from the position tonometers of the virtual image on the reticle plate. In conventional it is difficult to determine correctly and rapidly if proper alignment exists.
Also, it is designed as such that the anterior portion of the eye cannot be observed. Accordingly, the inspector of the eye has no way to recognize the state of the eye during the period of time from the aligning operation till the fluid discharge and thus inconvenient. For example, if the discharge of fluid takes place when the lid of the eye to be tested is closed, the obtained value of the intraocular pressure becomes unreliable.